Digital BW, The Print

B,

I don't think that is correct. As I understand things, a scanner with an 
optical resolution of 4800dpi can take a sample reading every 1/4800 of an 
inch. If you scan at the optical resolution, that is what is does and you 
get 4800 readings per inch along that axis (usually a different resolution 
on the other axis).

If you scan at 1200dpi, the scanner usually either samples all the 4800 
possible data points per inch and throws three out of every four away, or 
only samples every fourth possible point. So you are only getting one 
quarter of the possible data from the film.

With Vuescan software, you can set it to scan all 4800 data points per inch, 
but then to take the average of every four data points and reduce them to 
one, so that the file you get out is the equivalent of a 1200dpi scan, but 
all the data points have contributed to the final result.

I'm open to correction from any scanner experts.

Bob Frost.

----- Original Message ----- 
From: "B. Campbell" <bellis60@...>




Thanks, I understand and agree that "data amount" (i.e.size of file) depends
on the ppi of the scan and that you obviously will have a smaller file (i.e.
less "data") if you scan at smaller ppi. But that's a much different
statement than saying that scanning at a fourth of the resolution of which
the scanner is capable will result in the scanner "throwing away" three
fourths of the "detail in the film. " In fact the scanner doesn't "throw
away" anything in the film by scanning at a smaller ppi.. It just creates a
smaller file (i.e. fewer pixels, less "data") than could have been produced
had the scan been made at a higher ppi, which may or may not matter
depending on the size of the print.